1. Field of the Invention
The present invention relates to a surface mount antenna and an antenna module used for a radio communication device such as mobile phone.
2. Background Art
As shown in FIG. 28, a surface mount antenna has been known in the past, the antenna being configured such that a feed radiation conductor 101 as a main radiation element (feed element), and a parasitic radiation conductor 102 as a parasitic element are adjacently disposed on a surface of a dielectric substrate 100 having a rectangular shape. The feed radiation conductor 101 has one end 101A being connected to a signal source 103 to supply power from a side of the one end 101A, and has the other end 101B formed to be an open end (signal radiation side). The parasitic radiation conductor 102 has one end 102A being short-circuited, and has the other end 102B formed to be an open end (signal radiation side). The feed radiation conductor 101 and the parasitic radiation conductor 102 have different resonance length from each other. For example, as shown in an equivalent circuit of FIG. 29, the feed radiation conductor 101 is formed to have a length of λ1/4 (resonance frequency f1), and the parasitic radiation conductor 102 is formed to have a length of λ2/4 (resonance frequency f2) shorter than the length of λ1/4. In the surface mount antenna, power is supplied from the signal source 103 to the one end 101A of the feed radiation conductor 101, and power is supplied to the parasitic radiation conductor 102 via the feed radiation conductor 101 by electromagnetic coupling. In the surface mount antenna, the feed radiation conductor 101 and the parasitic radiation conductor 102 are double-resonated so as to secure a required frequency band.
Japanese Unexamined Patent Publication No. 2003-08326 discloses a surface mount antenna in a configuration where a feed radiation conductor and a parasitic radiation conductor are formed in a ring shape respectively in the same plane. Japanese Unexamined Patent Publication No. 2003-51705 discloses a surface mount antenna in a configuration where a feed radiation conductor and a parasitic radiation conductor are patterned such that respective open ends of the conductors are not adjacently disposed, but disposed away from each other.